1. Field of the Invention
The present invention is generally related to the control of an internal combustion engine in which nitrous oxide (N2O) is injected into the air intake manifold and, more particularly, to a method for more accurately calculating the appropriate fuel per cycle (FPC) as a function of an equivalent air charge, or air per cylinder (APCequiv), that would provide the same amount of oxygen as the actual mixed charge of both air and nitrous oxide.
2. Description of the Prior Art
It is well known to those skilled in the art that internal combustion engines can have nitrous oxide injected into their intake manifolds in order to boost the torque output of the engine. In most known cases of nitrous oxide injection, the nitrous oxide gas is injected into the air intake manifold of the engine without concern regarding the precise changes to the optimum fueling requirements that are caused by this injection of nitrous oxide. However, many different types of nitrous oxide injection systems are known to those skilled in the art.
U.S. Pat. No. 6,349,709, which issued to Evert et al on Feb. 26, 2002, describes a valve apparatus and method for injecting nitrous oxide into a combustion engine. An improved injection valve apparatus for variably controlling the injection of nitrous oxide and supplemental fuel into a combustion engine is described. In addition, a method for controlling and varying the amounts of nitrous oxide and supplemental fuel injected into a combustion engine based on existing engine conditions is discussed. The method programs engine parameters for the timing and volume of nitrous oxide injected into the engine, continuously monitors engine performance and engine conditions, and adjusts the amount of nitrous oxide injected and additional fuel supplied in response to changing engine conditions.
U.S. Pat. No. 6,260,546, which issued to Vaughn on Jul. 17, 2001, describes a direct nitrous injection system that is operable from zero to 100% throttle control. A supplemental nitrous oxide and fuel injection system for use with an internal combustion engine, which includes the unique properties of variable flow rate control of the supplemental injection system and direct cylinder injection methods is described. Where an engine is normally controlled by the driver with the zero to 100% throttle control of the existing air/fuel system, the supplemental nitrous oxide and fuel injection system is linked to the existing throttle control and controlled in the same manner. In addition, this system also provides a direct cylinder injection method that completely bypasses the existing intake manifold and carburetor/fuel injection.
U.S. Pat. No. 5,444,628, which issued to Meaney et al on Aug. 22, 1995, describes a computer controlled flow of nitrous oxide injected into an internal combustion engine. An engine system that is selectively powered by an enhanced air/fuel mixture is described. The supply of fuel to the cylinders of an internal combustion is increased in response to the addition of a supplemental oxidizing agent into an air/fuel mixture. The additional fuel may be added by increasing the duty cycle of fuel injectors mounted proximate the individual cylinders. In addition, the ignition timing is adjusted in accordance with the change in the density of the air/fuel mixture. The amount of supplemental oxidizing agent provided to the cylinders may be regulated by increasing in a controlled manner the rate at which the supplemental oxidizing agent is supplied over a period of time. Furthermore, the control unit for the engine receives and responds to a number of external operating parameters including the oxygen content of the engine exhaust and the traction of the tires.
U.S. Pat. No. 5,269,275, which issued to Dahlgren on Dec. 14, 1993, describes a pulse width modulated controller for nitrous oxide and fuel delivery. A pulse width modulated controller for nitrous oxide and enrichment fuel delivery includes a system control logic section which processes signals from sensors for throttle position, engine speed, and a number of other user selectable parameters and a driver selection controls electrically operated injectors or solenoid valves. The driver section allows the injectors to open only when all of the parameters sensed in the control section are met. Moreover, the driver section activates injectors according to a pulse generated by a pulse width modulation section which determines how long the injectors will remain activated. The pulse width modulation section receives signals based on the present throttle position and engine speed and adjusts these values according to values for nitrous oxide and enrichment fuel based on engine speed and throttle position set by the user in a tuning section and thereby continuously provides the driver section with a pulse having a width proportional to the proper amount of nitrous oxide and enrichment fuel which should be delivered at any given time. In addition, the tuning section is also user settable to a maximum ignition timing adjustment and provides a signal proportional to ignition timing retard to an ignition control section for automatically adjusting ignition timing according to the amount of nitrous oxide and enrichment fuel begin delivered at any given moment.
U.S. Pat. No. 4,494,488, which issued to Wheatley on Jan. 22, 1985, describes a fuel charging system for high performance vehicles. A fuel charging system injects liquid nitrous oxide into the engine of a high performance vehicle to provide an instant burst of power to the vehicle. A supply cylinder of pressurized liquid nitrous oxide is connected by an outlet conduit to the vehicle engine. A cylinder of nitrogen gas under a considerably higher pressure than that of the nitrous oxide is connected to the nitrous oxide cylinder by an inlet conduit. The nitrogen gas inlet conduit and nitrous oxide outlet conduit are connected to the nitrous oxide cylinder by an adapter valve. The nitrous gas passes through a pressure regulator located in the inlet conduit and maintains a high pressure blanket of gas above the nitrous oxide in the cylinder to force the nitrous oxide from the cylinder and into the engine at a constant and sustained rate eliminating the heretofore rapid drop in the supply pressure of the nitrous oxide as the supply of nitrous oxide is dissipated from the supply cylinder.
U.S. Pat. No. 5,848,582, which issued to Ehlers et al on Dec. 15, 1998, discloses an internal combustion engine with barometric pressure related start of air compensation for a fuel injector. A control system for a fuel injector system for an internal combustion engine is provided with a method by which the magnitude of the start of air point for the injector system is modified according to the barometric pressure in a region surrounding the engine. This offset, or modification, of the start of air point adjusts the timing of the fuel injector system to suit different altitudes at which the engine may be operating.
U.S. Pat. No. 6,250,292, which issued to Suhre on Jun. 26, 2001, discloses a method of controlling an engine with a pseudo throttle position sensor value. In the event that a throttle sensor fails, a method is provided which allows a pseudo throttle position sensor value to be calculated as a function of volumetric efficiency, pressure, volume, temperature, and the ideal gas constant. This is accomplished by first determining an air per cylinder (APC) value and then calculating the mass air flow into the engine as a function of the air per cylinder value. The mass air flow is then used, as a ratio of the maximum mass air flow at maximum power at sea level for the engine, to calculate a pseudo throttle position sensor value. That pseudo TPS (BARO) value is then used to select an air/fuel target ratio that allows the control system to calculate the fuel per cycle (FPC) for the engine.
U.S. Pat. No. 6,298,824, which issued to Suhre on Oct. 9, 2001, discloses an engine control system using an air and fuel control strategy based on torque demand. A control system for a fuel injected engine provides an engine control unit that receives signals from a throttle handle that is manually manipulated by an operator of a marine vessel. The engine control unit also measures engine speed and various other parameters, such as manifold absolute pressure, temperature, barometric pressure, and throttle position. The engine control unit controls the timing of fuel injectors and the injection system and also controls the position of a throttle plate. No direct connection is provided between a manually manipulated throttle handle and the throttle plate. All operating parameters are either calculated as a function of ambient conditions or determined by selecting parameters from matrices which allow the engine control unit to set the operating parameters as a function of engine speed and torque demand, as represented by the position of the throttle handle.
U.S. Pat. No. 6,378,506, which issued to Suhre et al on Apr. 30, 2002, discloses a control system for an engine supercharging system. A bypass control valve is controlled by an engine control module as a function of manifold absolute pressure and temperature within an air intake manifold in conjunction with the barometric pressure. An air per cylinder (APC) magnitude is calculated dynamically and compared to a desired APC value which is selected as a function of engine operating parameters. The air per cylinder value is calculated as a function of the manifold absolute pressure, the cylinder swept volume, the volumetric efficiency, the ideal gas constant, and the air inlet temperature. The volumetric efficiency is selected from stored data as a function of engine speed and a ratio of manifold absolute pressure to barometric pressure.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When an internal combustion engine is provided with a nitrous oxide injection system, it is advisable that the fuel per cycle (FPC) be modified to maintain the appropriate the air/fuel mixture. It would be significantly beneficial if a system could be provided that accurately calculates the effect, on the oxygen intake of the engine, caused by the injection of nitrous oxide and then calculates the necessary fuel per cylinder (FPC) based on that calculated value of effective oxygen provided to the cylinders during each cylinder event.
A method for controlling an internal combustion engine, in accordance with the preferred embodiment of the present invention, comprises the steps of directing a stream of air to a cylinder of an internal combustion engine and injecting a gas into the stream of air upstream from the cylinder. It further comprises the steps of determining the effective mass of gas flowing into the cylinder during every complete cycle of a piston which is disposed for reciprocating movement within the cylinder and calculating a mass of air quantity that is equivalent to the effective mass of gas, as a function of the magnitude of oxygen provided into the cylinder. It also comprises the step of determining a quantity of fuel to be injected into the stream of air as a function of the mass of air quantity that is equivalent to the effective mass of gas resulting from the calculating step.
The directing step is accomplished by providing an air intake manifold through which air is directed from the ambient surroundings of the internal combustion engine to the cylinder. The injecting step comprises the step of injecting nitrous oxide into the air stream.
The step of determining the effective mass of gas flowing into the cylinder comprises the steps of measuring the pressure (MAP) within an air intake manifold of the internal combustion engine and measuring the temperature of the stream of air flowing through the air intake manifold. The step of determining the effective mass of gas flowing into the cylinder can also comprise the step of determining a volumetric efficiency value as a function of the operating speed of the internal combustion engine, the barometric pressure and the pressure within an air intake manifold of the internal combustion engine.
The method of the present invention can further comprise the step of modifying the volumetric efficiency as a function of the measured temperature within the air intake manifold of the internal combustion engine.